feat(misc): add /gacha Genshin-style wish picker

Options take an optional *4 or *5 rarity tag; untagged options are 3 stars.
A pick rolls a tier at Genshin base rates over the tiers present, then an
option uniformly within it, so untagged input matches /random. The wish
animation renders as MP4 on the wheelofnames service at /api/gacha, with a
text fallback when the renderer is unset or fails.

.env.example

@@ -38,8 +38,9 @@ STICKER_PACK_NAME=miti99_by_miti99bot
 # Without it every /lol* fetch fails; the stale cache covers ≤60 min.
 LOL_PANDASCORE_TOKEN=
 
-# Optional /wheelofnames GIF renderer. Standard deployment:
-# https://github.com/tiennm99/wheelofnames. Leave blank to fall back to text
+# Optional /wheelofnames GIF and /gacha MP4 renderer. Standard deployment:
+# https://github.com/tiennm99/wheelofnames. Set the full /api/gif endpoint;
+# /gacha calls /api/gacha on the same service. Leave blank to fall back to text
 # selection.
 WHEELOFNAMES_API_URL=
 # Bearer token matching the wheelofnames service API_TOKEN when URL is set.